Network Working Group H. Kennedy
Request for Comments: 3252 Mimezine
Category: Informational 1 April 2002
Binary Lexical Octet Ad-hoc Transport
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document defines a reformulation of IP and two transport layer
protocols (TCP and UDP) as XML applications.
1. Introduction
1.1. Overview
This document describes the Binary Lexical Octet Ad-hoc Transport
(BLOAT): a reformulation of a widely-deployed network-layer protocol
(IP [RFC791]), and two associated transport layer protocols (TCP
[RFC793] and UDP [RFC768]) as XML [XML] applications. It also
describes methods for transporting BLOAT over Ethernet and IEEE 802
networks as well as encapsulating BLOAT in IP for gatewaying BLOAT
across the public Internet.
1.2. Motivation
The wild popularity of XML as a basis for application-level protocols
such as the Blocks Extensible Exchange Protocol [RFC3080], the Simple
Object Access Protocol [SOAP], and Jabber [JABBER] prompted
investigation into the possibility of extending the use of XML in the
protocol stack. Using XML at both the transport and network layer in
addition to the application layer would provide for an amazing amount
of power and flexibility while removing dependencies on proprietary
and hard-to-understand binary protocols. This protocol unification
would also allow applications to use a single XML parser for all
aspects of their operation, eliminating developer time spent figuring
out the intricacies of each new protocol, and moving the hard work of
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parsing to the XML toolset. The use of XML also mitigates concerns
over "network vs. host" byte ordering which is at the root of many
network application bugs.
1.3. Relation to Existing Protocols
The reformulations specified in this RFC follow as closely as
possible the spirit of the RFCs on which they are based, and so MAY
contain elements or attributes that would not be needed in a pure
reworking (e.g. length attributes, which are implicit in XML.)
The layering of network and transport protocols are maintained in
this RFC despite the optimizations that could be made if the line
were somewhat blurred (i.e. merging TCP and IP into a single, larger
element in the DTD) in order to foster future use of this protocol as
a basis for reformulating other protocols (such as ICMP.)
Other than the encoding, the behavioral aspects of each of the
existing protocols remain unchanged. Routing, address spaces, TCP
congestion control, etc. behave as specified in the extant standards.
Adapting to new standards and experimental algorithm heuristics for
improving performance will become much easier once the move to BLOAT
has been completed.
1.4. Requirement Levels
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
2. IPoXML
This protocol MUST be implemented to be compliant with this RFC.
IPoXML is the root protocol REQUIRED for effective use of TCPoXML
(section 3.) and higher-level application protocols.
The DTD for this document type can be found in section 7.1.
The routing of IPoXML can be easily implemented on hosts with an XML
parser, as the regular structure lends itself handily to parsing and
validation of the document/datagram and then processing the
destination address, TTL, and checksum before sending it on to its
next-hop.
The reformulation of IPv4 was chosen over IPv6 [RFC2460] due to the
wider deployment of IPv4 and the fact that implementing IPv6 as XML
would have exceeded the 1500 byte Ethernet MTU.
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All BLOAT implementations MUST use - and specify - the UTF-8 encoding
of RFC 2279 [RFC2279]. All BLOAT document/datagrams MUST be well-
formed and include the XMLDecl.
2.1. IP Description
A number of items have changed (for the better) from the original IP
specification. Bit-masks, where present have been converted into
human-readable values. IP addresses are listed in their dotted-
decimal notation [RFC1123]. Length and checksum values are present
as decimal integers.
To calculate the length and checksum fields of the IP element, a
canonicalized form of the element MUST be used. The canonical form
SHALL have no whitespace (including newline characters) between
elements and only one space character between attributes. There
SHALL NOT be a space following the last attribute in an element.
An iterative method SHOULD be used to calculate checksums, as the
length field will vary based on the size of the checksum.
The payload element bears special attention. Due to the character
set restrictions of XML, the payload of IP datagrams (which MAY
contain arbitrary data) MUST be encoded for transport. This RFC
REQUIRES the contents of the payload to be encoded in the base-64
encoding of RFC 2045 [RFC2045], but removes the requirement that the
encoded output MUST be wrapped on 76-character lines.
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2.2. Example Datagram
The following is an example IPoXML datagram with an empty payload:
3. TCPoXML
This protocol MUST be implemented to be compliant with this RFC. The
DTD for this document type can be found in section 7.2.
3.1. TCP Description
A number of items have changed from the original TCP specification.
Bit-masks, where present have been converted into human-readable
values. Length and checksum and port values are present as decimal
integers.
To calculate the length and checksum fields of the TCP element, a
canonicalized form of the element MUST be used as in section 2.1.
An iterative method SHOULD be used to calculate checksums as in
section 2.1.
The payload element MUST be encoded as in section 2.1.
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The TCP offset element was expanded to a maximum of 255 from 16 to
allow for the increased size of the header in XML.
TCPoXML datagrams encapsulated by IPoXML MAY omit the header
as well as the declaration.
3.2. Example Datagram
The following is an example TCPoXML datagram with an empty payload:
4. UDPoXML
This protocol MUST be implemented to be compliant with this RFC. The
DTD for this document type can be found in section 7.3.
4.1. UDP Description
A number of items have changed from the original UDP specification.
Bit-masks, where present have been converted into human-readable
values. Length and checksum and port values are present as decimal
integers.
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To calculate the length and checksum fields of the UDP element, a
canonicalized form of the element MUST be used as in section 2.1. An
iterative method SHOULD be used to calculate checksums as in section
2.1.
The payload element MUST be encoded as in section 2.1.
UDPoXML datagrams encapsulated by IPoXML MAY omit the header
as well as the declaration.
4.2. Example Datagram
The following is an example UDPoXML datagram with an empty payload:
5. Network Transport
This document provides for the transmission of BLOAT datagrams over
two common families of physical layer transport. Future RFCs will
address additional transports as routing vendors catch up to the
specification, and we begin to see BLOAT routed across the Internet
backbone.
5.1. Ethernet
BLOAT is encapsulated in Ethernet datagrams as in [RFC894] with the
exception that the type field of the Ethernet frame MUST contain the
value 0xBEEF. The first 5 octets of the Ethernet frame payload will
be 0x3c 3f 78 6d 6c ("
RFC 3252 Binary Lexical Octet Ad-hoc Transport 1 April 2002
6. Gatewaying over IP
In order to facilitate the gradual introduction of BLOAT into the
public Internet, BLOAT MAY be encapsulated in IP as in [RFC2003] to
gateway between networks that run BLOAT natively on their LANs.
7. DTDs
The Transport DTDs (7.2. and 7.3.) build on the definitions in the
Network DTD (7.1.)
The DTDs are referenced by their PubidLiteral and SystemLiteral (from
[XML]) although it is understood that most IPoXML implementations
will not need to pull down the DTD, as it will normally be embedded
in the implementation, and presents something of a catch-22 if you
need to load part of your network protocol over the network.
7.1. IPoXML DTD
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reserved CDATA #FIXED "0"
df (may|dont) #REQUIRED
mf (last|more) #REQUIRED>
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7.2. TCPoXML DTD
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7.3. UDPoXML DTD
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8. Security Considerations
XML, as a subset of SGML, has the same security considerations as
specified in SGML Media Types [RFC1874]. Security considerations
that apply to IP, TCP and UDP also likely apply to BLOAT as it does
not attempt to correct for issues not related to message format.
9. References
[JABBER] Miller, J., "Jabber", draft-miller-jabber-00.txt,
February 2002. (Work in Progress)
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC894] Hornig, C., "Standard for the Transmission of IP
Datagrams over Ethernet Networks.", RFC 894, April 1984.
[RFC1042] Postel, J. and J. Reynolds, "Standard for the
Transmission of IP Datagrams Over IEEE 802 Networks", STD
43, RFC 1042, February 1988.
[RFC1123] Braden, R., "Requirements for Internet Hosts -
Application and Support", RFC 1123, October 1989.
[RFC1874] Levinson, E., "SGML Media Types", RFC 1874, December
1995.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
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[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3080] Rose, M., "The Blocks Extensible Exchange Protocol Core",
RFC 3080, March 2001.
[SOAP] Box, D., Ehnebuske, D., Kakivaya, G., Layman, A.,
Mendelsohn, N., Nielsen, H. F., Thatte, S. Winer, D.,
"Simple Object Access Protocol (SOAP) 1.1" World Wide Web
Consortium Note, May 2000 http://www.w3.org/TR/SOAP/
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C. M., "Extensible
Markup Language (XML)" World Wide Web Consortium
Recommendation REC- xml-19980210.
http://www.w3.org/TR/1998/REC-xml-19980210
10. Author's Address
Hugh Kennedy
Mimezine
1060 West Addison
Chicago, IL 60613
USA
EMail: kennedyh@engin.umich.edu
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11. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
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included on all such copies and derivative works. However, this
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the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
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followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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